The invention relates to an assembly apparatus for nuclear reactors, consisting of two rope drums, two gear mechanisms, and two hoisting mechanisms each with one rope for a predetermined load, a change-speed gear mechanism or shiftable gear mechanism for the selectable adjustment of various hoisting speeds for the two hoisting mechanisms, a drive connection which is provided for at least one gear mechanism and permits different distances between the said gear mechanism and the change-speed gear mechanism, a common motor for the two hoisting mechanisms, a rigid connection for the two lifting mechanisms which permits different distances between the lifting mechanisms, and a rope compensating device selectively adjustable so as to be operative or inoperative.
In the assembly of a nuclear reactor and in the subsequent operation of the completed reactor, a hoisting device is needed and the requirements of the device differ widely from one case to another and can in principle be divided into two classes, namely:
Requirements in respect of the hoisting device during the erection of a reactor plant, and requirements in respect of the hoisting device during the actual operation of the reactor or for repair work or work for the replacement of parts of the reactor plant.
In the course of the erection of a reactor plant, the pressure vessel and the heat exchangers, for example, must be brought into the required positions. In nuclear reactors the weight of a pressure vessel amounts to about 500 metric tons; in order to simplify explanations hereinbelow this load will be referred to as 2P. The heat exchangers are generally of substantially cylindrical shape and of relatively great length. This leads to difficulties in determining the height of the hoisting device, since the effective height cannot be made sufficiently high to connect the heat exchanger at its top part to the tackle to a hoisting device to move the heat exchanger over previously completed parts of the foundation or other parts of the reactor which have already been installed. The procedure has therefore been adopted in the assembly work of holding the heat exchanger in the region of its upper half by means of a frame or a yoke, which in turn is suspended on two pulley blocks belonging to two separate trolleys, each of which is capable of lifting a load P. The working speed at which the heat exchanger is raised and lowered is relatively low because of the size and bulky nature of the heat exchanger; in order to simplify the explanations given below this lifting speed will be referred to as V/2.
If hoisting work has to be done during the subsequent operation of the reactor the maximum load to be lifted is the load P, for example when the heat exchanger inserts have to be exchanged. Hoisting work in the assembly of the reactor is however subject to particularly stringent safety regulations, which have been laid down in a "Notice regarding safety requirements for hoisting and conveying equipment in nuclear reactor plants". According to these regulations, two ropes independent of one another must be used for the hoisting device, each of them being able to lift the load P, while in the operating condition only one of the ropes is loaded at any given time, and the other rope is provided without bearing loads in order to be ready for use in the event of the fracture of the first rope, or else a double degree of safety per rope can be achieved by means of two ropes equally sharing the load.
Erection work in nuclear reactor plants has hitherto been carried out in the following manner. For the purpose of erection or assembly use was made of a trolley, which is subsequently used as operating trolley, and of an assembly trolley which is used solely for assembly work and is removed on completion of the assembly. Each of the two trolleys has its own drive motor ropes, gearing, rope drum, and the like, each of the two ropes of the operating trolley and the rope of the assembly trolley being designed for the load P. As already stated, the assembly trolley is not required for the subsequent operation, when the operating trolley only is used. Since on completion of the installation the assembly trolley is removed, this results in the disadvantage that subsequent replacement of the pressure vessel or of the heat exchanger makes it necessary for the assembly trolley to be installed again, since for the load of 2P the additional power for the motor of the assembly trolley is required. In addition the load is too high, and therefore cannot be carried by the tackle.